The present invention relates to a new and improved construction of apparatus for building a rotationally symmetrically evened bobbin package with a bobbin chuck for supporting the bobbin and with a friction drive drum for driving the bobbin and also pertains to a method of operating the apparatus.
The equipment and methods known thus far for building rotationally symmetrically evened bobbin packages using a friction drive drum as a drive element are based on winding devices, the bobbins of which rotate in a range of rotational speeds below the critical rotational speed or critical speed which is realized by rigidly mounting the bobbin chuck support bearings and by using bobbin chucks of correspondingly massive design.
The critical speed or critical rotational speed, as such terms are used herein, is understood to mean the rotational speed of a shaft at which some periodic disturbing force coincides with the fundamental or some higher mode of the natural frequency or torsional or transverse vibration of the shaft and its attached masses.
Massive bobbin chucks, or bobbin chucks of large diameter, respectively, however possess the disadvantages that they require the use of bobbin tubes of large diameters, which not only are heavier and more expensive but also take-up less yarn package weight at a given outside diameter of the completed bobbin package and furthermore, the large bearing diameters required by the large bobbin tube diameters cause frequent difficulties at high rotational speeds, not even considering the high price of such large bearings.
A further disadvantage of an operational range of rotational speeds below the critical rotational speed resides in the fact that, while taking into account a maximum bobbin tube diameter as determined by economic considerations, the maximum winding speed is likewise limited, and hence the production capacity is also limited. Furthermore, the bobbin package weight obtainable at speeds below the critical rotational speed must be correspondingly limited which also is considered disadvantageous.
As increased production rates are required it is the objective to increase the winding speeds to 3,000 meters per minute and higher, which, if economically feasible bobbin tube diameters and bobbin weights are to be used, requires that the bobbin chucks rotate at speeds above the critical rotational speeds.
High rotational speeds of the bobbin chucks, however, also require improved concentricity of the rotational movement of the friction drive drums which also rotate at higher speeds in order that detrimental influences are kept to a minimum upon the rotationally symmetrically even bobbin package build.
Practical experience, however, has shown that when using a bobbin chuck operated at speeds above the critical rotational speed, it is not possible to obtain a satisfactory bobbin package build or formation without additional measures or precautions, since the conditions of movement are such that a one-sided deformation of the bobbin is favored.